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Network+ lab 2 of 27

Packets on the wire: OSI layers and traffic types

Capture real traffic with tcpdump and take it apart layer by layer: ARP broadcasts, ICMP, a TCP three-way handshake carrying HTTP, a UDP datagram and OSPF multicast. You see encapsulation change at each router hop and learn the ports the exam lists.

Run this lab

It needs Lite: its 5 nodes are set to 5 vCPU and 3,328 MB in total. That fits the free demo too.

In your workspace: Shared, then CompTIA Network Plus N10-009 guided labs, then 02 - Packets on the wire - OSI layers and traffic types

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Level
Beginner
Time
About 50 minutes
Nodes need
5 vCPU, 3,328 MB
Smallest plan
Lite

The scenario

Harbour Logistics' intranet web server H2 sits on its own segment behind router R1. Users on the office LAN reach it through R1. Before the security team rolls out encryption, they want someone to show them, packet by packet, what actually crosses the wire. You'll capture on H2, the server, and take the traffic apart layer by layer.

DeviceInterfaceAddressConnects to
R1Gi0/010.10.10.1/24SW1 Gi0/0 (office LAN)
R1Gi0/110.10.20.1/24H2 eth0 (server segment)
H1eth0DHCP (10.10.10.100 upwards)SW1 Gi0/1
PC1eth010.10.10.50/24SW1 Gi0/2
H2eth010.10.20.20/24, gateway .1R1 Gi0/1

What you’ll practise

  • Capture and filter traffic with tcpdump, live and to a file
  • Identify layer 2, 3 and 4 headers in a capture and explain encapsulation
  • Show that MAC addresses change at each router hop while IP addresses stay the same
  • Recognise a TCP three-way handshake and compare it with connectionless UDP
  • Tell unicast, broadcast and multicast traffic apart
  • Match common services to their well-known ports

The tasks

  • Task 0: Prepare the web server H2
  • Task 1: Capture ARP and ICMP, and read the layers
  • Task 2: Watch the frame change at the router
  • Task 3: Capture a TCP three-way handshake and HTTP
  • Task 4: Send a UDP datagram
  • Task 5: Make R1 send multicast
  • Task 6: Ports and services
  • Ports the exam expects you to know

The Lab Tasks pane has the scenario, these tasks, the checks to run, hints and the full solution.

Topology and devices

The network as it opens in EVE-NG, drawn from the lab’s own canvas, and the image each node runs.

Topology of Packets on the wire - OSI layers and traffic types5 nodes, 4 links. Every link is listed as text below the diagram.R1SW1H1PC1H2Gi0/1eth0Gi0/2eth0Gi0/0Gi0/0Gi0/1eth0
5 nodes, with the interface names each link uses. On a narrow screen, scroll the diagram sideways.
Every link, as text
  • SW1 Gi0/0 to R1 Gi0/0
  • SW1 Gi0/1 to H1 eth0
  • SW1 Gi0/2 to PC1 eth0
  • R1 Gi0/1 to H2 eth0
Nodes in Packets on the wire: OSI layers and traffic types, with the image each runs and the vCPU and RAM it’s set to
NodeDeviceImage in Add NodeSet to
R1Cisco IOSvvios-adventerprisek9-m.SPA.159-3.M61 vCPU, 512 MB
SW1Cisco IOSvL2viosl2-adventerprisek9-m.ssa.high_iron_202009291 vCPU, 768 MB
H1Alpine Linuxclbalpinebase-alpine-base-3-20-31 vCPU, 512 MB
PC1VPCS hostBuilt in to EVE-NGCounted as 1 vCPU, 1,024 MB
H2Alpine Linuxclbalpinebase-alpine-base-3-20-31 vCPU, 512 MB

How to open this lab

  1. Sign in to your workspace at lab.cloudlabbox.com.

  2. In File Manager, open Shared, then the folder CompTIA Network Plus N10-009 guided labs.

  3. Open 02 - Packets on the wire - OSI layers and traffic types and start its nodes, then open Lab Tasks for the scenario and the steps.

The lab is read-only. You can start the nodes and configure the devices, but changes to the topology can’t be saved. To change it, rebuild it in your own folder.

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CloudLabBox is independent of CompTIA, Cisco and Netgate. The lab follows exam topics and isn’t vendor training material; vendor names identify the exams and the images in the workspace.